Traditional compounds of the morphine type act at the level of the Mu receptors, but have the drawback of causing troublesome side effects (phenomena of physical and mental dependence, respiratory depression, etc.), in consequence of which it is hazardous to use such products in some subjects.
Products which are more specific for the Kappa receptors exhibit a potent analgesic activity without causing the side effects of traditional morphine type compounds.
Amides derived from phenothiazine of general formula: ##STR2## in which R is, in particular, a hydrogen atom, had been described in U.S. Pat. No. 3,112,310 in connection with their activity with respect to the central nervous system.